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If A : B = 3 : 4 and B : C = 6 : 5, then A : B : C equals:
A9 : 12 : 10
B3 : 4 : 5
C18 : 24 : 20
D6 : 8 : 5
Answer & Solution
Correct answer: A. 9 : 12 : 10
1. B must carry the same value in both ratios before they can be joined.
2. B is 4 in the first and 6 in the second; the LCM of 4 and 6 is 12.
3. Scale the first by 3: A : B = 9 : 12.
4. Scale the second by 2: B : C = 12 : 10.
5. Joining them gives A : B : C = 9 : 12 : 10. Option C is the same ratio unsimplified, but 9 : 12 : 10 has no common factor, so it is the required form.
_Source: NCERT Class 8 Maths, Ch 7 'Comparing Quantities', S7.1 Recalling Ratios and Percentages_
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